Just had a tanking job done in back reception. They put the taking slurry up to about 4ft then plaster boarded it . It was going the plaster dried out. Then we got heavy rain and round circles have appeared on the plaster boards on chimney breast and by back window. Once I put the humidifier on they were gone in 10 mins.
Does this mean the tanking has not worked or could it be condensation etc.
Its a 1950s 3 story house with cavity wall.